Factual error: There is no way that Brian could have crossed underneath a tractor trailer the way that he did on the freeway scene. The speed of the truck, moving fast at least at 60 or 65 miles an hour on a California highway, would have struck and run him over immediately had he tried to duck underneath its cargo like that on a skateboard.
Factual error: After the passenger door gets ripped off the Oldsmobile Toronado, a female voice is heard repeating that the "passenger door is ajar." While the Toronado was available with an optional Voice Alert system, the GM system used a male voice.
Answer: More than likely, it was probably something made up and meaningless. But of course, we would never know because it's Vietnamese. The best you can do is have a Vietnamese person view that part of the film and get them to translate it if it was actually a real sentence being spoken, which I doubt.